CO2 Question

Hi all,
I have a 4X4X8 grow room with one 1000W HPS and a can fan for exhaust and a seperate 4inch for intake. I have just baught a 20lbs co2 tank with regulator and selonoide.

My question is: Should I stop my exhaust fan while I am throwing in my co2? Won't it go out the window?

I was thinking of letting the co2 sit for about 30 minutes, then turn back on exhaust for about an hour, then send back co2 inside for another 30 mins. and so on.

What do you think? Have any better ideas?
Thanks

Definitely want to turn off exaust. Dont want to suck out what you just paid for. Try to raise your temp up to around 85, then give it the CO2.